[ViewVC] Diff of: cvs/cvsroot/AnyEvent-MP/MP.pm

Comparing cvsroot/AnyEvent-MP/MP.pm (file contents):
Revision 1.54 by root, Fri Aug 14 16:15:37 2009 UTC vs.
Revision 1.72 by root, Mon Aug 31 10:07:04 2009 UTC

…		…
11	NODE $port # returns the noderef of the port	11	NODE $port # returns the noderef of the port
12		12
13	$SELF # receiving/own port id in rcv callbacks	13	$SELF # receiving/own port id in rcv callbacks
14		14
15	# initialise the node so it can send/receive messages	15	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	16	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		17
20	# ports are message endpoints	18	# ports are message endpoints
21		19
22	# sending messages	20	# sending messages
23	snd $port, type => data...;	21	snd $port, type => data...;
…		…
40	mon $port, $otherport # kill otherport on abnormal death	38	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	39	mon $port, $otherport, @msg # send message on death
42		40
43	=head1 CURRENT STATUS	41	=head1 CURRENT STATUS
44		42
		43	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	44	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	45	AnyEvent::MP::Intro - uptodate, but incomplete.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	46	AnyEvent::MP::Kernel - mostly stable.
		47	AnyEvent::MP::Global - stable API, protocol not yet final.
49		48
50	stay tuned.	49	stay tuned.
51		50
52	=head1 DESCRIPTION	51	=head1 DESCRIPTION
53		52
54	This module (-family) implements a simple message passing framework.	53	This module (-family) implements a simple message passing framework.
55		54
56	Despite its simplicity, you can securely message other processes running	55	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	56	on the same or other hosts, and you can supervise entities remotely.
58		57
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	58	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	59	manual page and the examples under F<eg/>.
61		60
62	At the moment, this module family is severly broken and underdocumented,	61	At the moment, this module family is a bit underdocumented.
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		62
66	=head1 CONCEPTS	63	=head1 CONCEPTS
67		64
68	=over 4	65	=over 4
69		66
70	=item port	67	=item port
71		68
72	A port is something you can send messages to (with the C<snd> function).	69	A port is something you can send messages to (with the C<snd> function).
73		70
74	Ports allow you to register C<rcv> handlers that can match all or just	71	Ports allow you to register C<rcv> handlers that can match all or just
75	some messages. Messages will not be queued.	72	some messages. Messages send to ports will not be queued, regardless of
		73	anything was listening for them or not.
76		74
77	=item port id - C<noderef#portname>	75	=item port ID - C<nodeid#portname>
78		76
79	A port ID is the concatenation of a noderef, a hash-mark (C<#>) as	77	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
80	separator, and a port name (a printable string of unspecified format). An	78	separator, and a port name (a printable string of unspecified format).
81	exception is the the node port, whose ID is identical to its node
82	reference.
83		79
84	=item node	80	=item node
85		81
86	A node is a single process containing at least one port - the node port,	82	A node is a single process containing at least one port - the node port,
87	which provides nodes to manage each other remotely, and to create new	83	which enables nodes to manage each other remotely, and to create new
88	ports.	84	ports.
89		85
90	Nodes are either private (single-process only), slaves (connected to a	86	Nodes are either public (have one or more listening ports) or private
91	master node only) or public nodes (connectable from unrelated nodes).	87	(no listening ports). Private nodes cannot talk to other private nodes
		88	currently.
92		89
93	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	90	=item node ID - C<[a-za-Z0-9_\-.:]+>
94		91
95	A node reference is a string that either simply identifies the node (for	92	A node ID is a string that uniquely identifies the node within a
96	private and slave nodes), or contains a recipe on how to reach a given	93	network. Depending on the configuration used, node IDs can look like a
97	node (for public nodes).	94	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		95	doesn't interpret node IDs in any way.
98		96
99	This recipe is simply a comma-separated list of C<address:port> pairs (for	97	=item binds - C<ip:port>
100	TCP/IP, other protocols might look different).
101		98
102	Node references come in two flavours: resolved (containing only numerical	99	Nodes can only talk to each other by creating some kind of connection to
103	addresses) or unresolved (where hostnames are used instead of addresses).	100	each other. To do this, nodes should listen on one or more local transport
		101	endpoints - binds. Currently, only standard C<ip:port> specifications can
		102	be used, which specify TCP ports to listen on.
104		103
105	Before using an unresolved node reference in a message you first have to	104	=item seeds - C<host:port>
106	resolve it.	105
		106	When a node starts, it knows nothing about the network. To teach the node
		107	about the network it first has to contact some other node within the
		108	network. This node is called a seed.
		109
		110	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		111	are expected to be long-running, and at least one of those should always
		112	be available. When nodes run out of connections (e.g. due to a network
		113	error), they try to re-establish connections to some seednodes again to
		114	join the network.
		115
		116	Apart from being sued for seeding, seednodes are not special in any way -
		117	every public node can be a seednode.
107		118
108	=back	119	=back
109		120
110	=head1 VARIABLES/FUNCTIONS	121	=head1 VARIABLES/FUNCTIONS
111		122
…		…
126	use base "Exporter";	137	use base "Exporter";
127		138
128	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	139	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
129		140
130	our @EXPORT = qw(	141	our @EXPORT = qw(
131	NODE $NODE *SELF node_of _any_	142	NODE $NODE *SELF node_of after
132	resolve_node initialise_node	143	configure
133	snd rcv mon kil reg psub spawn	144	snd rcv mon mon_guard kil reg psub spawn
134	port	145	port
135	);	146	);
136		147
137	our $SELF;	148	our $SELF;
138		149
…		…
142	kil $SELF, die => $msg;	153	kil $SELF, die => $msg;
143	}	154	}
144		155
145	=item $thisnode = NODE / $NODE	156	=item $thisnode = NODE / $NODE
146		157
147	The C<NODE> function returns, and the C<$NODE> variable contains the	158	The C<NODE> function returns, and the C<$NODE> variable contains, the node
148	noderef of the local node. The value is initialised by a call to	159	ID of the node running in the current process. This value is initialised by
149	C<initialise_node>.	160	a call to C<configure>.
150		161
151	=item $noderef = node_of $port	162	=item $nodeid = node_of $port
152		163
153	Extracts and returns the noderef from a port ID or a noderef.	164	Extracts and returns the node ID from a port ID or a node ID.
154		165
155	=item initialise_node $noderef, $seednode, $seednode...	166	=item configure key => value...
156		167
157	=item initialise_node "slave/", $master, $master...
158
159	Before a node can talk to other nodes on the network it has to initialise	168	Before a node can talk to other nodes on the network (i.e. enter
160	itself - the minimum a node needs to know is it's own name, and optionally	169	"distributed mode") it has to configure itself - the minimum a node needs
161	it should know the noderefs of some other nodes in the network.	170	to know is its own name, and optionally it should know the addresses of
		171	some other nodes in the network to discover other nodes.
162		172
163	This function initialises a node - it must be called exactly once (or	173	This function configures a node - it must be called exactly once (or
164	never) before calling other AnyEvent::MP functions.	174	never) before calling other AnyEvent::MP functions.
165		175
166	All arguments (optionally except for the first) are noderefs, which can be
167	either resolved or unresolved.
168
169	The first argument will be looked up in the configuration database first
170	(if it is C<undef> then the current nodename will be used instead) to find
171	the relevant configuration profile (see L<aemp>). If none is found then
172	the default configuration is used. The configuration supplies additional
173	seed/master nodes and can override the actual noderef.
174
175	There are two types of networked nodes, public nodes and slave nodes:
176
177	=over 4	176	=over 4
178		177
179	=item public nodes	178	=item step 1, gathering configuration from profiles
180		179
181	For public nodes, C<$noderef> (supplied either directly to	180	The function first looks up a profile in the aemp configuration (see the
182	C<initialise_node> or indirectly via a profile or the nodename) must be a	181	L<aemp> commandline utility). The profile name can be specified via the
183	noderef (possibly unresolved, in which case it will be resolved).	182	named C<profile> parameter. If it is missing, then the nodename (F<uname
		183	-n>) will be used as profile name.
184		184
185	After resolving, the node will bind itself on all endpoints and try to	185	The profile data is then gathered as follows:
186	connect to all additional C<$seednodes> that are specified. Seednodes are
187	optional and can be used to quickly bootstrap the node into an existing
188	network.
189		186
190	=item slave nodes	187	First, all remaining key => value pairs (all of which are conviniently
		188	undocumented at the moment) will be interpreted as configuration
		189	data. Then they will be overwritten by any values specified in the global
		190	default configuration (see the F<aemp> utility), then the chain of
		191	profiles chosen by the profile name (and any C<parent> attributes).
191		192
192	When the C<$noderef> (either as given or overriden by the config file)	193	That means that the values specified in the profile have highest priority
193	is the special string C<slave/>, then the node will become a slave	194	and the values specified directly via C<configure> have lowest priority,
194	node. Slave nodes cannot be contacted from outside and will route most of	195	and can only be used to specify defaults.
195	their traffic to the master node that they attach to.
196		196
197	At least one additional noderef is required (either by specifying it	197	If the profile specifies a node ID, then this will become the node ID of
198	directly or because it is part of the configuration profile): The node	198	this process. If not, then the profile name will be used as node ID. The
199	will try to connect to all of them and will become a slave attached to the	199	special node ID of C<anon/> will be replaced by a random node ID.
200	first node it can successfully connect to.	200
		201	=item step 2, bind listener sockets
		202
		203	The next step is to look up the binds in the profile, followed by binding
		204	aemp protocol listeners on all binds specified (it is possible and valid
		205	to have no binds, meaning that the node cannot be contacted form the
		206	outside. This means the node cannot talk to other nodes that also have no
		207	binds, but it can still talk to all "normal" nodes).
		208
		209	If the profile does not specify a binds list, then a default of C<*> is
		210	used, meaning the node will bind on a dynamically-assigned port on every
		211	local IP address it finds.
		212
		213	=item step 3, connect to seed nodes
		214
		215	As the last step, the seeds list from the profile is passed to the
		216	L<AnyEvent::MP::Global> module, which will then use it to keep
		217	connectivity with at least one node at any point in time.
201		218
202	=back	219	=back
203		220
204	This function will block until all nodes have been resolved and, for slave	221	Example: become a distributed node using the locla node name as profile.
205	nodes, until it has successfully established a connection to a master	222	This should be the most common form of invocation for "daemon"-type nodes.
206	server.
207		223
208	Example: become a public node listening on the guessed noderef, or the one	224	configure
209	specified via C<aemp> for the current node. This should be the most common
210	form of invocation for "daemon"-type nodes.
211		225
212	initialise_node;	226	Example: become an anonymous node. This form is often used for commandline
		227	clients.
213		228
214	Example: become a slave node to any of the the seednodes specified via	229	configure nodeid => "anon/";
215	C<aemp>. This form is often used for commandline clients.
216		230
217	initialise_node "slave/";	231	Example: configure a node using a profile called seed, which si suitable
		232	for a seed node as it binds on all local addresses on a fixed port (4040,
		233	customary for aemp).
218		234
219	Example: become a slave node to any of the specified master servers. This	235	# use the aemp commandline utility
220	form is also often used for commandline clients.	236	# aemp profile seed setnodeid anon/ setbinds '*:4040'
221		237
222	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	238	# then use it
		239	configure profile => "seed";
223		240
224	Example: become a public node, and try to contact some well-known master	241	# or simply use aemp from the shell again:
225	servers to become part of the network.	242	# aemp run profile seed
226		243
227	initialise_node undef, "master1", "master2";	244	# or provide a nicer-to-remember nodeid
228		245	# aemp run profile seed nodeid "$(hostname)"
229	Example: become a public node listening on port C<4041>.
230
231	initialise_node 4041;
232
233	Example: become a public node, only visible on localhost port 4044.
234
235	initialise_node "localhost:4044";
236
237	=item $cv = resolve_node $noderef
238
239	Takes an unresolved node reference that may contain hostnames and
240	abbreviated IDs, resolves all of them and returns a resolved node
241	reference.
242
243	In addition to C<address:port> pairs allowed in resolved noderefs, the
244	following forms are supported:
245
246	=over 4
247
248	=item the empty string
249
250	An empty-string component gets resolved as if the default port (4040) was
251	specified.
252
253	=item naked port numbers (e.g. C<1234>)
254
255	These are resolved by prepending the local nodename and a colon, to be
256	further resolved.
257
258	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
259
260	These are resolved by using AnyEvent::DNS to resolve them, optionally
261	looking up SRV records for the C<aemp=4040> port, if no port was
262	specified.
263
264	=back
265		246
266	=item $SELF	247	=item $SELF
267		248
268	Contains the current port id while executing C<rcv> callbacks or C<psub>	249	Contains the current port id while executing C<rcv> callbacks or C<psub>
269	blocks.	250	blocks.
270		251
271	=item SELF, %SELF, @SELF...	252	=item *SELF, SELF, %SELF, @SELF...
272		253
273	Due to some quirks in how perl exports variables, it is impossible to	254	Due to some quirks in how perl exports variables, it is impossible to
274	just export C<$SELF>, all the symbols called C<SELF> are exported by this	255	just export C<$SELF>, all the symbols named C<SELF> are exported by this
275	module, but only C<$SELF> is currently used.	256	module, but only C<$SELF> is currently used.
276		257
277	=item snd $port, type => @data	258	=item snd $port, type => @data
278		259
279	=item snd $port, @msg	260	=item snd $port, @msg
280		261
281	Send the given message to the given port ID, which can identify either	262	Send the given message to the given port, which can identify either a
282	a local or a remote port, and must be a port ID.	263	local or a remote port, and must be a port ID.
283		264
284	While the message can be about anything, it is highly recommended to use a	265	While the message can be almost anything, it is highly recommended to
285	string as first element (a port ID, or some word that indicates a request	266	use a string as first element (a port ID, or some word that indicates a
286	type etc.).	267	request type etc.) and to consist if only simple perl values (scalars,
		268	arrays, hashes) - if you think you need to pass an object, think again.
287		269
288	The message data effectively becomes read-only after a call to this	270	The message data logically becomes read-only after a call to this
289	function: modifying any argument is not allowed and can cause many	271	function: modifying any argument (or values referenced by them) is
290	problems.	272	forbidden, as there can be considerable time between the call to C<snd>
		273	and the time the message is actually being serialised - in fact, it might
		274	never be copied as within the same process it is simply handed to the
		275	receiving port.
291		276
292	The type of data you can transfer depends on the transport protocol: when	277	The type of data you can transfer depends on the transport protocol: when
293	JSON is used, then only strings, numbers and arrays and hashes consisting	278	JSON is used, then only strings, numbers and arrays and hashes consisting
294	of those are allowed (no objects). When Storable is used, then anything	279	of those are allowed (no objects). When Storable is used, then anything
295	that Storable can serialise and deserialise is allowed, and for the local	280	that Storable can serialise and deserialise is allowed, and for the local
296	node, anything can be passed.	281	node, anything can be passed. Best rely only on the common denominator of
		282	these.
297		283
298	=item $local_port = port	284	=item $local_port = port
299		285
300	Create a new local port object and returns its port ID. Initially it has	286	Create a new local port object and returns its port ID. Initially it has
301	no callbacks set and will throw an error when it receives messages.	287	no callbacks set and will throw an error when it receives messages.
…		…
388		374
389	sub rcv($@) {	375	sub rcv($@) {
390	my $port = shift;	376	my $port = shift;
391	my ($noderef, $portid) = split /#/, $port, 2;	377	my ($noderef, $portid) = split /#/, $port, 2;
392		378
393	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	379	$NODE{$noderef} == $NODE{""}
394	or Carp::croak "$port: rcv can only be called on local ports, caught";	380	or Carp::croak "$port: rcv can only be called on local ports, caught";
395		381
396	while (@_) {	382	while (@_) {
397	if (ref $_[0]) {	383	if (ref $_[0]) {
398	if (my $self = $PORT_DATA{$portid}) {	384	if (my $self = $PORT_DATA{$portid}) {
…		…
477	$res	463	$res
478	}	464	}
479	}	465	}
480	}	466	}
481		467
482	=item $guard = mon $port, $cb->(@reason)	468	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
483		469
484	=item $guard = mon $port, $rcvport	470	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
485		471
486	=item $guard = mon $port	472	=item $guard = mon $port # kill $SELF when $port dies
487		473
488	=item $guard = mon $port, $rcvport, @msg	474	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
489		475
490	Monitor the given port and do something when the port is killed or	476	Monitor the given port and do something when the port is killed or
491	messages to it were lost, and optionally return a guard that can be used	477	messages to it were lost, and optionally return a guard that can be used
492	to stop monitoring again.	478	to stop monitoring again.
493		479
494	C<mon> effectively guarantees that, in the absence of hardware failures,	480	C<mon> effectively guarantees that, in the absence of hardware failures,
495	that after starting the monitor, either all messages sent to the port	481	after starting the monitor, either all messages sent to the port will
496	will arrive, or the monitoring action will be invoked after possible	482	arrive, or the monitoring action will be invoked after possible message
497	message loss has been detected. No messages will be lost "in between"	483	loss has been detected. No messages will be lost "in between" (after
498	(after the first lost message no further messages will be received by the	484	the first lost message no further messages will be received by the
499	port). After the monitoring action was invoked, further messages might get	485	port). After the monitoring action was invoked, further messages might get
500	delivered again.	486	delivered again.
		487
		488	Note that monitoring-actions are one-shot: once messages are lost (and a
		489	monitoring alert was raised), they are removed and will not trigger again.
501		490
502	In the first form (callback), the callback is simply called with any	491	In the first form (callback), the callback is simply called with any
503	number of C<@reason> elements (no @reason means that the port was deleted	492	number of C<@reason> elements (no @reason means that the port was deleted
504	"normally"). Note also that I<< the callback B<must> never die >>, so use	493	"normally"). Note also that I<< the callback B<must> never die >>, so use
505	C<eval> if unsure.	494	C<eval> if unsure.
…		…
567	is killed, the references will be freed.	556	is killed, the references will be freed.
568		557
569	Optionally returns a guard that will stop the monitoring.	558	Optionally returns a guard that will stop the monitoring.
570		559
571	This function is useful when you create e.g. timers or other watchers and	560	This function is useful when you create e.g. timers or other watchers and
572	want to free them when the port gets killed:	561	want to free them when the port gets killed (note the use of C<psub>):
573		562
574	$port->rcv (start => sub {	563	$port->rcv (start => sub {
575	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	564	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
576	undef $timer if 0.9 < rand;	565	undef $timer if 0.9 < rand;
577	});	566	});
578	});	567	});
579		568
580	=cut	569	=cut
…		…
589		578
590	=item kil $port[, @reason]	579	=item kil $port[, @reason]
591		580
592	Kill the specified port with the given C<@reason>.	581	Kill the specified port with the given C<@reason>.
593		582
594	If no C<@reason> is specified, then the port is killed "normally" (linked	583	If no C<@reason> is specified, then the port is killed "normally" (ports
595	ports will not be kileld, or even notified).	584	monitoring other ports will not necessarily die because a port dies
		585	"normally").
596		586
597	Otherwise, linked ports get killed with the same reason (second form of	587	Otherwise, linked ports get killed with the same reason (second form of
598	C<mon>, see below).	588	C<mon>, see above).
599		589
600	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	590	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
601	will be reported as reason C<< die => $@ >>.	591	will be reported as reason C<< die => $@ >>.
602		592
603	Transport/communication errors are reported as C<< transport_error =>	593	Transport/communication errors are reported as C<< transport_error =>
…		…
608	=item $port = spawn $node, $initfunc[, @initdata]	598	=item $port = spawn $node, $initfunc[, @initdata]
609		599
610	Creates a port on the node C<$node> (which can also be a port ID, in which	600	Creates a port on the node C<$node> (which can also be a port ID, in which
611	case it's the node where that port resides).	601	case it's the node where that port resides).
612		602
613	The port ID of the newly created port is return immediately, and it is	603	The port ID of the newly created port is returned immediately, and it is
614	permissible to immediately start sending messages or monitor the port.	604	possible to immediately start sending messages or to monitor the port.
615		605
616	After the port has been created, the init function is	606	After the port has been created, the init function is called on the remote
617	called. This function must be a fully-qualified function name	607	node, in the same context as a C<rcv> callback. This function must be a
618	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	608	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
619	program, use C<::name>.	609	specify a function in the main program, use C<::name>.
620		610
621	If the function doesn't exist, then the node tries to C<require>	611	If the function doesn't exist, then the node tries to C<require>
622	the package, then the package above the package and so on (e.g.	612	the package, then the package above the package and so on (e.g.
623	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	613	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
624	exists or it runs out of package names.	614	exists or it runs out of package names.
625		615
626	The init function is then called with the newly-created port as context	616	The init function is then called with the newly-created port as context
627	object (C<$SELF>) and the C<@initdata> values as arguments.	617	object (C<$SELF>) and the C<@initdata> values as arguments.
628		618
629	A common idiom is to pass your own port, monitor the spawned port, and	619	A common idiom is to pass a local port, immediately monitor the spawned
630	in the init function, monitor the original port. This two-way monitoring	620	port, and in the remote init function, immediately monitor the passed
631	ensures that both ports get cleaned up when there is a problem.	621	local port. This two-way monitoring ensures that both ports get cleaned up
		622	when there is a problem.
632		623
633	Example: spawn a chat server port on C<$othernode>.	624	Example: spawn a chat server port on C<$othernode>.
634		625
635	# this node, executed from within a port context:	626	# this node, executed from within a port context:
636	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	627	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
666	my $id = "$RUNIQ." . $ID++;	657	my $id = "$RUNIQ." . $ID++;
667		658
668	$_[0] =~ /::/	659	$_[0] =~ /::/
669	or Carp::croak "spawn init function must be a fully-qualified name, caught";	660	or Carp::croak "spawn init function must be a fully-qualified name, caught";
670		661
671	($NODE{$noderef} \|\| add_node $noderef)	662	snd_to_func $noderef, "AnyEvent::MP::_spawn" => $id, @_;
672	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
673		663
674	"$noderef#$id"	664	"$noderef#$id"
675	}	665	}
676		666
677	=back	667	=item after $timeout, @msg
678		668
679	=head1 NODE MESSAGES	669	=item after $timeout, $callback
680		670
681	Nodes understand the following messages sent to them. Many of them take	671	Either sends the given message, or call the given callback, after the
682	arguments called C<@reply>, which will simply be used to compose a reply	672	specified number of seconds.
683	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
684	the remaining arguments are simply the message data.
685		673
686	While other messages exist, they are not public and subject to change.	674	This is simply a utility function that comes in handy at times - the
		675	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		676	so it may go away in the future.
687		677
688	=over 4
689
690	=cut	678	=cut
691		679
692	=item lookup => $name, @reply	680	sub after($@) {
		681	my ($timeout, @action) = @_;
693		682
694	Replies with the port ID of the specified well-known port, or C<undef>.	683	my $t; $t = AE::timer $timeout, 0, sub {
695		684	undef $t;
696	=item devnull => ...	685	ref $action[0]
697		686	? $action[0]()
698	Generic data sink/CPU heat conversion.	687	: snd @action;
699		688	};
700	=item relay => $port, @msg	689	}
701
702	Simply forwards the message to the given port.
703
704	=item eval => $string[ @reply]
705
706	Evaluates the given string. If C<@reply> is given, then a message of the
707	form C<@reply, $@, @evalres> is sent.
708
709	Example: crash another node.
710
711	snd $othernode, eval => "exit";
712
713	=item time => @reply
714
715	Replies the the current node time to C<@reply>.
716
717	Example: tell the current node to send the current time to C<$myport> in a
718	C<timereply> message.
719
720	snd $NODE, time => $myport, timereply => 1, 2;
721	# => snd $myport, timereply => 1, 2, <time>
722		690
723	=back	691	=back
724		692
725	=head1 AnyEvent::MP vs. Distributed Erlang	693	=head1 AnyEvent::MP vs. Distributed Erlang
726		694
…		…
736		704
737	Despite the similarities, there are also some important differences:	705	Despite the similarities, there are also some important differences:
738		706
739	=over 4	707	=over 4
740		708
741	=item * Node references contain the recipe on how to contact them.	709	=item * Node IDs are arbitrary strings in AEMP.
742		710
743	Erlang relies on special naming and DNS to work everywhere in the	711	Erlang relies on special naming and DNS to work everywhere in the same
744	same way. AEMP relies on each node knowing it's own address(es), with	712	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
745	convenience functionality.	713	configuraiton or DNS), but will otherwise discover other odes itself.
746
747	This means that AEMP requires a less tightly controlled environment at the
748	cost of longer node references and a slightly higher management overhead.
749		714
750	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	715	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
751	uses "local ports are like remote ports".	716	uses "local ports are like remote ports".
752		717
753	The failure modes for local ports are quite different (runtime errors	718	The failure modes for local ports are quite different (runtime errors
…		…
782		747
783	Erlang makes few guarantees on messages delivery - messages can get lost	748	Erlang makes few guarantees on messages delivery - messages can get lost
784	without any of the processes realising it (i.e. you send messages a, b,	749	without any of the processes realising it (i.e. you send messages a, b,
785	and c, and the other side only receives messages a and c).	750	and c, and the other side only receives messages a and c).
786		751
787	AEMP guarantees correct ordering, and the guarantee that there are no	752	AEMP guarantees correct ordering, and the guarantee that after one message
788	holes in the message sequence.	753	is lost, all following ones sent to the same port are lost as well, until
789		754	monitoring raises an error, so there are no silent "holes" in the message
790	=item * In Erlang, processes can be declared dead and later be found to be	755	sequence.
791	alive.
792
793	In Erlang it can happen that a monitored process is declared dead and
794	linked processes get killed, but later it turns out that the process is
795	still alive - and can receive messages.
796
797	In AEMP, when port monitoring detects a port as dead, then that port will
798	eventually be killed - it cannot happen that a node detects a port as dead
799	and then later sends messages to it, finding it is still alive.
800		756
801	=item * Erlang can send messages to the wrong port, AEMP does not.	757	=item * Erlang can send messages to the wrong port, AEMP does not.
802		758
803	In Erlang it is quite likely that a node that restarts reuses a process ID	759	In Erlang it is quite likely that a node that restarts reuses a process ID
804	known to other nodes for a completely different process, causing messages	760	known to other nodes for a completely different process, causing messages
…		…
808	around in the network will not be sent to an unrelated port.	764	around in the network will not be sent to an unrelated port.
809		765
810	=item * Erlang uses unprotected connections, AEMP uses secure	766	=item * Erlang uses unprotected connections, AEMP uses secure
811	authentication and can use TLS.	767	authentication and can use TLS.
812		768
813	AEMP can use a proven protocol - SSL/TLS - to protect connections and	769	AEMP can use a proven protocol - TLS - to protect connections and
814	securely authenticate nodes.	770	securely authenticate nodes.
815		771
816	=item * The AEMP protocol is optimised for both text-based and binary	772	=item * The AEMP protocol is optimised for both text-based and binary
817	communications.	773	communications.
818		774
819	The AEMP protocol, unlike the Erlang protocol, supports both	775	The AEMP protocol, unlike the Erlang protocol, supports both programming
820	language-independent text-only protocols (good for debugging) and binary,	776	language independent text-only protocols (good for debugging) and binary,
821	language-specific serialisers (e.g. Storable).	777	language-specific serialisers (e.g. Storable). By default, unless TLS is
		778	used, the protocol is actually completely text-based.
822		779
823	It has also been carefully designed to be implementable in other languages	780	It has also been carefully designed to be implementable in other languages
824	with a minimum of work while gracefully degrading fucntionality to make the	781	with a minimum of work while gracefully degrading functionality to make the
825	protocol simple.	782	protocol simple.
826		783
827	=item * AEMP has more flexible monitoring options than Erlang.	784	=item * AEMP has more flexible monitoring options than Erlang.
828		785
829	In Erlang, you can chose to receive I<all> exit signals as messages	786	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
832	Erlang, as one can choose between automatic kill, exit message or callback	789	Erlang, as one can choose between automatic kill, exit message or callback
833	on a per-process basis.	790	on a per-process basis.
834		791
835	=item * Erlang tries to hide remote/local connections, AEMP does not.	792	=item * Erlang tries to hide remote/local connections, AEMP does not.
836		793
837	Monitoring in Erlang is not an indicator of process death/crashes,	794	Monitoring in Erlang is not an indicator of process death/crashes, in the
838	as linking is (except linking is unreliable in Erlang).	795	same way as linking is (except linking is unreliable in Erlang).
839		796
840	In AEMP, you don't "look up" registered port names or send to named ports	797	In AEMP, you don't "look up" registered port names or send to named ports
841	that might or might not be persistent. Instead, you normally spawn a port	798	that might or might not be persistent. Instead, you normally spawn a port
842	on the remote node. The init function monitors the you, and you monitor	799	on the remote node. The init function monitors you, and you monitor the
843	the remote port. Since both monitors are local to the node, they are much	800	remote port. Since both monitors are local to the node, they are much more
844	more reliable.	801	reliable (no need for C<spawn_link>).
845		802
846	This also saves round-trips and avoids sending messages to the wrong port	803	This also saves round-trips and avoids sending messages to the wrong port
847	(hard to do in Erlang).	804	(hard to do in Erlang).
848		805
849	=back	806	=back
850		807
851	=head1 RATIONALE	808	=head1 RATIONALE
852		809
853	=over 4	810	=over 4
854		811
855	=item Why strings for ports and noderefs, why not objects?	812	=item Why strings for port and node IDs, why not objects?
856		813
857	We considered "objects", but found that the actual number of methods	814	We considered "objects", but found that the actual number of methods
858	thatc an be called are very low. Since port IDs and noderefs travel over	815	that can be called are quite low. Since port and node IDs travel over
859	the network frequently, the serialising/deserialising would add lots of	816	the network frequently, the serialising/deserialising would add lots of
860	overhead, as well as having to keep a proxy object.	817	overhead, as well as having to keep a proxy object everywhere.
861		818
862	Strings can easily be printed, easily serialised etc. and need no special	819	Strings can easily be printed, easily serialised etc. and need no special
863	procedures to be "valid".	820	procedures to be "valid".
864		821
865	And a a miniport consists of a single closure stored in a global hash - it	822	And as a result, a miniport consists of a single closure stored in a
866	can't become much cheaper.	823	global hash - it can't become much cheaper.
867		824
868	=item Why favour JSON, why not real serialising format such as Storable?	825	=item Why favour JSON, why not a real serialising format such as Storable?
869		826
870	In fact, any AnyEvent::MP node will happily accept Storable as framing	827	In fact, any AnyEvent::MP node will happily accept Storable as framing
871	format, but currently there is no way to make a node use Storable by	828	format, but currently there is no way to make a node use Storable by
872	default.	829	default (although all nodes will accept it).
873		830
874	The default framing protocol is JSON because a) JSON::XS is many times	831	The default framing protocol is JSON because a) JSON::XS is many times
875	faster for small messages and b) most importantly, after years of	832	faster for small messages and b) most importantly, after years of
876	experience we found that object serialisation is causing more problems	833	experience we found that object serialisation is causing more problems
877	than it gains: Just like function calls, objects simply do not travel	834	than it solves: Just like function calls, objects simply do not travel
878	easily over the network, mostly because they will always be a copy, so you	835	easily over the network, mostly because they will always be a copy, so you
879	always have to re-think your design.	836	always have to re-think your design.
880		837
881	Keeping your messages simple, concentrating on data structures rather than	838	Keeping your messages simple, concentrating on data structures rather than
882	objects, will keep your messages clean, tidy and efficient.	839	objects, will keep your messages clean, tidy and efficient.
883		840
884	=back	841	=back
885		842
886	=head1 SEE ALSO	843	=head1 SEE ALSO
887		844
		845	L<AnyEvent::MP::Intro> - a gentle introduction.
		846
		847	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		848
		849	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		850	your applications.
		851
888	L<AnyEvent>.	852	L<AnyEvent>.
889		853
890	=head1 AUTHOR	854	=head1 AUTHOR
891		855
892	Marc Lehmann <schmorp@schmorp.de>	856	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.72 by root, Mon Aug 31 10:07:04 2009 UTC